The photosensitive element is used mainly for forming a circuit on a printed wiring board. In addition, the photosensitive element is also used in the formation of an insulating film for protecting the circuit on the printed wiring board, in the formation of a spacer for keeping a gap between liquid crystal layers in a liquid crystal display device constant, and in the like.
The photosensitive element usually has a three-layer structure of a support film, a photosensitive layer and a protective film. The photosensitive element is used in the following way, for instance. Firstly, the protective film of the photosensitive element is peeled off, and then the photosensitive layer which contains a photosensitive resin composition is laminated on a substrate (lamination step). Next, a predetermined portion of the photosensitive layer is irradiated with active rays from the support film side to form a photo-cured portion (light exposure step). After that, the support film is peeled and removed, then an unexposed portion is removed (developed) from the substrate, and thereby a resist pattern, which is composed of a cured product of the photosensitive resin composition, is formed on the substrate (development step).
The obtained resist pattern can be used for an insulating film, a spacer or the like, and can also be used as a mask for forming a circuit by plating treatment or etching treatment for the resist pattern.
By the way, in the present technical field, it is known that there is the case where the shape of the contact surface with the photosensitive layer in the protective film is transferred onto the photosensitive layer. For instance, in the following Patent Document 1, it is shown that the air void, which occurs when the photosensitive layer is laminated, is reduced by adjusting a surface roughness (Ra) of the contact surface with the photosensitive layer in the protective film to 0.15 μm or less, and also by reducing the number of fisheyes which are contained in the protective film and have a diameter of 80 μm or more to 5 pieces/m2 or less.
In addition, in the following Patent Document 2, it is shown that the followability to an uneven substrate is enhanced by adjusting the surface roughness (Ra) of the protective film to 0.5 μm or more, and making the shape disappear by pressurization at the time of the lamination.
Furthermore, in the following Patent Document 3, it is shown that a photosensitive layer, in which there is no occurrence of the air void, can be laminated on a base material which is used for photo-nanoimprint and has fine unevenness thereon, by adjusting the Ra of the contact surface with the photosensitive layer in the protective film to 0.05 to 0.5 μm, in a photosensitive element which transfers the fine unevenness having the surface roughness of 0.01 to 2 μm.